Why is failsafe mode activated when engine appears to be not overheated

Are you going by the temp gauge on the dash to say it's overheating ? Did you hook up a scan tool an look at live data from the coolant temp sensor to the PCM/ECM - engine computer ? Use a infrared thermometer to check engine temp at the thermostat housing ? Don't remember how many gm instrument clusters i sent to be fixed . GM had a problem with stepper motors inside the instrument cluster , stepper motors control the gauges needles . 2003 to 2006 this was a problem . you mite think it's overheating whens it's not .
https://www.youtube.com/watch?v=oTm2oDx-_GM

Might be the water pump! Take it back and tell them they need to do it right.

How do you know that the head gasket is good? even with a bad thermostat it would not overheat in 3-5 min, a bad fan or relay would not make it overheat so fast , this sounds like a bad waterpump that has a bad impeller that does not circulate the coolant , but would not take coolant , if you are going through coolant and overheating that fast i would say head gasket but if you were not loosing coolant i would say to check the water pump impeller, i have seen them rust away or break,

would have repaced the thermastadt. most commen cause of those fans not turning on because thr thermostadt is not letting the hot water flow into the radeattor .by passing the wiring and relays can only lead to bigger problems , but you have proven your fans work. water just drizled out of the block cause you had no water in the house to the pump ( no water to pump) thermostadts, temp sensors or temp sending unit .simple check for themostadt fill up with all houses attached with rad cap off run engine fill rad as needed keep feeling top hose to radiator it should get hot all of the sudden thats your thermostadt opening( working) go to next step check sensors or sending unit. realy best if you get a haynes or chilton at the half priced book store or auto parts storeand go to trouble shooting for over heating

CODE 12- NO DISTRIBUTOR REFERENCE PULSES ECM. CODE 13- OXYGEN CIRCUIT. CODE 14- COOLANT SENSOR HIGH TEMP CODE 15- COOLANT SENSOR LOW TEMP. CODE 21 - THROTTLE POSITION SENSOR VOLTAGE HIGH.CODE 22 - THROTTLE POSITION SENSOR VOLTAGE LOW.CODE - 23 MIXTURE CONTROL SOLENOID.FOR CARBURETOR ENGINE. CODE 24 -VECHICLE SPEED SENSOR. CODE 32 - BARO CIRCUIT LOW.CODE 32 - FUEL INJECTED EGR VALVE VACUUM SWITCH SHORTED TO GROUND.OR EGR VALVE SOLENOID CIRCUIT OPEN. CODE 33 - MAP SENSOR.CODE 34 - VACUUM SENSOR OR MAP SENSOR.CODE 35 - IDLE SPEED CONTROL. CODE 41 - EST CIRCUIT. CODE 42 - ELECTRONIC SPARK TIMING.CODE 43 - ELECTRONIC SPARK CONTROL UNIT. CODE 44 - LEAN EXHAUST.CODE 45 - RICH EXHAUST. CODE 51 - PROM OR MEM CAL.CODE 52 - CALPAK. CODE 53 -EGR VALVE CARBURETED ENGINE THE EGR VALVE VACUUM SENSOR HAS RECEIVED IMPROPER EGR VACUUM. CODE 54 - M C SOLENOID CARBURETED ENGINE MIXTURE CONTROL SOLENOID SHORTED OR FAULTY ECM.CODE 54- FUEL INJECTED ENGINE FUEL PUMP VOLTAGE IS LOW.CODE 55 - ECM MAKE SURE PCM GROUND CONNECTIONS ARE TIGHT.IF OKAY.REPLACE THE ECM.

P0401 - EGR Flow Insufficient Detected The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum.

• Vacuum supply
• EGR valve stuck closed
• EGR valve leaks vacuum
• EGR flow path restricted
• EGRVR circuit shorted to PWR
• VREF open to DPF EGR sensor
• DPF EGR sensor downstream hose off or plugged
• EGRVR circuit open to PCM
• VPWR open to EGRVR solenoid
• DPF EGR sensor hoses both off
• DPF EGR sensor hoses reversed
• Damaged EGR orifice tube
• Damaged EGRVR solenoid
• Damaged PCM

P1299 - Cylinder Head Over Temperature Protection Active Indicates an engine overheat condition was detected by the cylinder head temperature (CHT) sensor. An FMEM Strategy called Fail-safe Cooling was activated to cool the engine.

• Engine cooling system concerns
• Low engine coolant level
• Base engine concerns

P0300 - Random Misfire The random misfire DTC indicates multiple cylinders are misfiring or the PCM cannot identify which cylinder is misfiring.

• Camshaft position sensor (CMP)
• Low fuel: less than 1/8 tank
• Stuck open EGR valve

P0443 - EVAP Control System Canister Purge Valve Circuit Malfunction The PCM monitors the EVAP canister purge valve circuit for an electrical failure. The test fails when the signal moves outside the minimum or maximum allowable calibrated parameters for a specified purge duty cycle by PCM command.

• VPWR circuit open
• EVAP canister purge valve circuit shorted to GND
• Damaged EVAP canister purge valve
• EVAP canister purge valve circuit open
• EVAP canister purge valve circuit shorted to VPWR
• Damaged PCM

P1451 - EVAP Control System Canister Vent Solenoid Circuit Malfunction Monitors the canister vent (CV) solenoid circuit for an electrical failure. The test fails when the signal moves outside the minimum or maximum allowable calibrated parameters for a specified canister vent duty cycle by PCM command.

• VPWR circuit open
• CV solenoid circuit shorted to PWR GND or CHASSIS GND
• Damaged CV solenoid
• CV solenoid circuit open
• CV solenoid circuit shorted to VPWR
• Damaged PCM

P1309 - Misfire Monitor Disabled When the misfire monitor is disabled, usually due to the input signal generated by the camshaft position (CMP) sensor, by sensing the passage of teeth from the CMP wheel.

• Camshaft position sensor
• Powertrain control module
• ECT, MAF, and CKP sensors

with the codes you have here I would look in the direction of the egr valve first because that will cause the bucking and stalling, and the misfires, but so will the canister vent solonoid. the misfire codes and the cylinder overtemp code could be from overheating or because if the misfires.

is the temp gauge going to hot? if so, it may be going into failsafe mode where it shuts off half the cylinders to protect the engine.

check your engine coolant temp sensor. It sends a signal to tunrn the cooling fan on.
Does the cooling fan come under the hood?
Does the cooling fan come on when you turn the a/c on?

report back.

Water pump. No question in my mind, water pump.

pull codes from on board diagnostics turn key on not running press and hold hot button on temp and off at same time till dash lights up write down codes respond with all computer codes i will help you determine prodlem and try to fix

Hi,

Whatever the reason for the engine siezing, it will be to your advantage to replace the radiator as debris may already be blocking a number of the lines.

As to the overheating, the most likely reason is a failed water pump (most likely), or a thermostat stuck closed (least likely), or a coolant leak (noticeable). Since engine would be replaced, the water pump and thermostat would also be replaced and the leak would be verified upon installation of the new engine.

Incidentally, I was made to understand that Hyundai warranties their drivetrain for 10 years or 100,000 miles. I believe the engine is a part of the overall drivetrain system.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

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